We discuss materials based on arrays of metallic magnetic cylindrical structures near ferromagnetic resonance with applied magnetic fields at microwave frequencies. We have found that the materials have a negative refraction index by combining the effective negative permittivity and permeability. Numerical finite-difference time-domain simulations were performed, after a very large number of geometries were swept. The simulations reveal that ferromagnetic cylinders, with diameters of 0.1 cm and 0.5 cm apart, and with periodic or random configurations, are left-handed materials with very small losses; i.e., with transmittivity practically unity or no loss. The way to obtain convenient structures and geometries is also discussed.
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